Decorative, ornamental, or jewelry articles having diffraction gratings

ABSTRACT

A first article has a surface bearing a diffraction grating that comprises a plurality of elevated regions and recessed regions and a reflective coating that provides reflective diffraction within the article but is sufficiently thick to prevent diffraction outside the article. Alternatively, the reflective coating can be arranged to also provide reflective diffraction outside the article. A second article has a surface bearing a diffraction grating that comprises a plurality of elevated regions and recessed regions. Either (i) at least a portion of each ridge, or (ii) at least portion of each trench, comprises a material differing with respect to its refractive index or with respect to its optical transmissivity.

BENEFIT CLAIMS TO RELATED APPLICATIONS

This application claims benefit of: (i) U.S. provisional App. No.61/003,434 filed Nov. 15, 2007, and (ii) U.S. provisional App. No.61/126,792 filed May 6, 2008. Each of said provisional applications ishereby incorporated by reference as if fully set forth herein.

BACKGROUND

The field of the present invention relates to jewelry and otherdecorative or ornamental articles. In particular, jewelry and otherdecorative or ornamental articles are disclosed herein that have arraysof diffraction gratings.

A variety of decorative or ornamental articles, including jewelry items,have been described that include one or more diffraction gratings. Someof these are described in:

-   U.S. Pat. No. 4,490,440 entitled “High technology jewelry and    fabrication of same” issued Dec. 25, 1984 to Reber;-   U.S. Pat. No. 4,604,329 entitled “High technology decorative    materials and fabrication of same” issued Aug. 5, 1986 to Reber;-   U.S. Pat. No. 4,725,511 entitled “High technology decorative    materials for watchfaces and fabrication of same” issued Feb. 16,    1988 to Reber;-   U.S. Pat. No. 5,612,102 entitled “Faceted jewelry ornament with    facet grooved for light diffraction” issued Mar. 18, 1997 to Nakama;-   U.S. Pat. No. 6,713,842 entitled “Mask for and method of forming a    character on a substrate” issued Mar. 30, 2004 to Manchester; and-   U.S. Pub. No. 2007/0157667 A1 entitled “Enhancing the optical    characteristics of a gemstone” published Jul. 12, 2007 in the name    of Maltezos et al.

None of those references discloses jewelry or other decorative orornamental articles having arrays of diffraction gratings, one or moreof which is arranged to diffract, at one or more designed diffractionangles, substantially white light or light having a desired colorcomposition. None of those references discloses jewelry or otherdecorative or ornamental articles having arrays of diffraction gratings,one or more of which is arranged to focus light it diffracts. None ofthose references discloses jewelry or other decorative or ornamentalarticles wherein light from a moving source is diffracted from adesigned succession of gratings of the array that are arranged on asubstantially planar surface of an article, e.g., so as to simulate theappearance of a three-dimensional faceted article illuminated by themoving light source or to provide a dynamically pleasing appearance.None of those references discloses jewelry or other decorative orornamental articles wherein diffracted light intensity varies amonggratings of the array that are arranged on a substantially planarsurface of an article, e.g., so as to simulate the appearance of athree-dimensional article illuminated by a light source. None of thosereferences discloses jewelry or other decorative or ornamental articleswherein light is scattered from boundary regions between gratings of thearray. None of those references discloses jewelry or other decorative orornamental articles having diffraction gratings formed in deformablelayers on a surface of a curved or faceted article.

It may be desirable to provide jewelry or other decorative or ornamentalarticles having arrays of diffraction gratings that exhibit one or moreof the aforementioned characteristics. In the creation of visuallypleasing decorative, ornamental, or jewelry articles utilizingdiffractive structures, it can be desirable to identify structures orfabrication methods that lead to robust, attractive, high-quality itemswhile limiting, reducing, or minimizing manufacturing costs. Variousdiffraction grating arrangements are disclosed herein that are amenableto lower-cost fabrication methods or result in high-quality or robustdecorative, ornamental, or jewelry articles bearing diffractiongratings.

The subject matter of the instant application may be related to that ofU.S. provisional App. No. 60/877,901 filed Dec. 29, 2006, U.S.provisional App. No. 60/918,383 filed Mar. 16, 2007, and U.S.non-provisional application Ser. No. 11/967,181 filed Dec. 29, 2007.Each of said applications is hereby incorporated by reference as iffully set forth herein.

The subject matter of the instant application may be related to that ofU.S. provisional App. No. 60/950,562 filed Jul. 18, 2007 and U.S.non-provisional application Ser. No. 12/175,459 filed Jul. 18, 2008.Each of said applications is hereby incorporated by reference as iffully set forth herein.

SUMMARY

A first article comprises a volume of a first dielectric material havingat least one surface bearing at least one optical diffraction grating.The first dielectric material is substantially transparent over at leasta portion of the visible electromagnetic spectrum. The diffractiongrating comprises a plurality of elevated regions and recessed regions.The diffraction grating further comprises a reflective coating formed onthe elevated regions and recessed regions. The reflective coating can besufficiently thick so as to substantially fill the recessed regions andcover the elevated regions and thereby substantially prevent diffractionby the elevated regions and recessed regions of light incident on thereflective coating from outside the first dielectric material.Alternatively, the article can further comprise a second dielectricmaterial on the grating that is sufficiently thick so as tosubstantially fill the recessed regions and cover the elevated regions.In that case the reflective layer is arranged so as to enablediffraction of light incident on the reflective coating through thesecond dielectric material.

A second article comprises at least one surface bearing at least oneoptical diffraction grating. The article comprises a first dielectricmaterial that is substantially transparent over at least a portion ofthe visible electromagnetic spectrum. The diffraction grating comprisesa plurality of elevated regions and recessed regions. Either (i) atleast a portion of each ridge, or (ii) at least portion of each trench,comprises a second material. The second dielectric material differs fromthe first dielectric material with respect to its refractive index orwith respect to its optical transparency (equivalently, opticaltransmissivity) over the transparent spectral region of the firstdielectric material.

Objects and advantages pertaining to decorative, ornamental, or jewelryarticles having diffraction gratings may become apparent upon referringto the exemplary embodiments illustrated in the drawings and disclosedin the following written description or appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are schematic plan and cross-sectional views,respectively, of a diffraction grating comprising a set of elevatedregions and recessed regions.

FIG. 2 is a schematic plan view of a diffractive article having multiplediffractive facets.

FIG. 3 is a schematic cross-sectional view of an exemplary diffractiongrating.

FIG. 4 is a schematic cross-sectional view of another exemplarydiffraction grating.

FIG. 5 is a schematic cross-sectional view of another exemplarydiffraction grating.

FIGS. 6A and 6B are schematic cross-sectional views of other exemplarydiffraction gratings.

FIG. 7 is a schematic cross-sectional view of another exemplarydiffraction grating.

FIG. 8 is a schematic cross-sectional view of another exemplarydiffraction grating on a faceted volume of dielectric material.

FIGS. 9A and 9B are schematic plan and cross-sectional views,respectively, of another exemplary diffraction grating between twovolumes of dielectric material.

FIG. 10 illustrate schematically a method for making an article with adiffraction gratings.

In many of the drawings, a diffraction grating is shown with a smallnumber of diffractive elements (i.e., grating “lines” or gratingridges/trenches), typically a half dozen or so up to perhaps a fewdozen. The number of grating lines shown is typically far smaller thanthe number of such lines that are actually present on an article (oftenmany dozens, hundreds, or more). The number of grating lines shown isreduced in number for clarity of illustration.

The embodiments shown in the drawings are exemplary, and should not beconstrued as limiting the scope of the present disclosure or appendedclaims.

DETAILED DESCRIPTION OF EMBODIMENTS

A centerpiece of many pieces of jewelry is a gemstone (diamond, cubiczirconium, etc.) that produces a pleasing visual appearance byreflecting or refracting incident light from one or more of a multitudeof facets. Some light reflected or refracted from the gemstone,particularly light that is reflected from an outer surface of a facetwithout being transmitted, exhibits no dispersion, i.e., all colorcomponents of the light are reflected in essentially the same manner. Aviewer whose eye catches such a reflection sees a color representativeof the spectrum of the incident light. For example, under typicalambient illumination conditions, the viewer would see white lightreflected from the gemstone; other illumination conditions would resultin correspondingly different reflected light being seen by the viewer.The sparkles of typically white light produced by facet reflectioncomprise the so-called brilliance of the gemstone. Light that enters thegemstone to reemerge (with or without internal reflection) can exhibitdispersion as a result of wavelength dependent refraction upontransmission through one or more facet surfaces, i.e., differingconstituent colors of the illuminating light emerge propagating alongdifferent output directions. Under white light illumination, a viewer ofsuch refracted light would typically see the light as colored becauseonly a portion of the spectral bandwidth of the illuminating spectrumwould enter his or her eye. Light emitted by the gemstone that hasexperienced dispersion comprises the gemstone's so-called fire, whichcomprises flashes of colored light observed as the viewer, gemstone, orlight source move relative to one another.

Both brilliance and fire are important in enabling a gemstone to producethe most pleasant viewing experience. This is similarly true in the caseof diffraction gratings or other diffractive structures used to enhancepackaging through the creation of attractive visual displays.

Disclosed in various of the incorporated references are jewelry or otherdecorative or ornamental articles having arrays of diffraction gratings(reflective or transmissive) for producing visual effects includingbrilliance, fire, or both that appear similar to those of high qualitygemstones. The array of diffraction gratings can be arranged so as toreproduce the appearance of facets, even on a substantially planarsurface of an article. The array of gratings can be arranged so that thediffracted light appears to emanate in a pleasing manner as from atraditional gemstone. The array of gratings can be arranged so as tocreate visual effects not found in traditional jewelry or gemstones, forexample, the distribution of facets may create visually pleasingpatterns that change dynamically (rotate, expand, deform, or otherwisechange) with changing relative positions of the observer, the articlewith the array of gratings, and one or more light sources. The array ofgratings can be arranged so as to incorporate an additional opticalattribute not found in typical gemstones, namely, a focusing attributeimparted onto light reflected or refracted by the article. The array ofgratings can be arranged so as to provide visibility over wide viewingareas or angles. The array of gratings can be combined with one or morerefractive elements, or can be attached to a curved surface, to form avisually pleasing article. For example, the placement of a faceteddielectric medium (e.g., glass, crystal, or plastic) over a diffractivesurface grating can enhance the perceived beauty of the article byincreasing (by refraction through the faceted medium) the number ofdirections from which diffracted light can be seen and by adding theperception of depth to the article. A grating positioned near or on onefacet of a faceted dielectric medium, even a single uniform gratingcovering an entire facet of the dielectric medium can dramaticallyenhance the fire observed through multiple of the facets of thedielectric medium.

Arrays of diffraction gratings exhibiting one or more of the attributesrecited in the preceding paragraph can be fabricated on the surface ofmetal jewelry articles (rings, earrings, brooches, pendants, braceletsand such) instead of or in addition to one or more gemstones, and can beused to create unusual visual effects enhancing the visual appeal ofsuch articles.

Diffraction gratings or other diffractive structures possessing at leastone of above attributes on a substantially transparent or reflectivesubstrate can be employed to create an attractive visual display forhome or workplace decoration, decorative packaging, posters, or otherdecorative or ornamental articles. If desired, such articles can bemass-produced on a polymer or other inexpensive substrate usingembossing, stamping, injection molding, or other suitable replicationtechnique.

A diffractive structure can deflect reflected or transmitted light so asto create a spatial separation of colors. A diffractive structure mayappear to an observer to shine in different colors as the relativepositions or orientations of the diffractive structure, operative lightsources, and the observer's eye change. The diffractive structure can bearranged so that such varying appearance can have a visually pleasingaspect, particularly if the diffractive structure comprises multiplefacets each of which has a diffraction grating differing from at leastsome of the other gratings with respect to one or more of its operativecharacteristics, e.g., diffractive contour spacing or grating linespacing, grating line orientation, grating line shape (e.g., straight orcurved), grating line cross-sectional structure (e.g., height, width, orcross-sectional shape of ridges forming the grating lines),reflectivity, transmissivity, or other optical qualities that affect themanner in which light is diffracted from a given diffraction grating. Ina diffractive structure with a multitude of diffraction gratings (i.e.,diffractive facets) having differing diffractive characteristics, anobserver may see a multitude of sparkles of differing color as thevarious facets move into and out of positions to diffract specificcolors toward the observer. The appearance of the multifaceteddiffractive structure can be tailored by judicious choice of the gratingattributes of the various facets.

In the creation of visually pleasing decorative, ornamental, or jewelryarticles utilizing diffractive structures, it can be desirable toidentify structures or fabrication methods that lead to robust,attractive, high-quality items while limiting, reducing, or minimizingmanufacturing costs. Various diffraction grating arrangements aredisclosed herein that are amenable to lower-cost fabrication methods orresult in high-quality or robust decorative, ornamental, or jewelryarticles bearing diffraction gratings. The disclosed gratingarrangements include transmissive, partially transmissive, reflective,and partially reflective diffraction gratings.

An exemplary transmissive diffraction grating is illustratedschematically in FIGS. 1A and 1B, which can represent a singlediffraction grating or a single diffractive facet of a multi-faceteddiffractive structure. The exemplary grating comprises a plurality ofelongated ridges 104 with intervening trenches or grooves 105. Moregenerally, a diffraction grating can comprises a plurality of spatialregions on a surface that are elevated (e.g., the ridges 104) relativeto adjacent, recessed spatial regions of that surface (e.g., thetrenches 105), with the elevated and recessed regions being arranged onthe surface to provide the desired diffractive behavior. While only afew ridges/trenches are shown in FIGS. 1A and 1B, typically hundreds orthousands are be present in a typical diffraction grating. For atransmissive grating, the ridges 104 and trenches 105 are formed in oron a substantially transparent substrate 103, which can comprise glass(of various suitable types), quartz, silica, sapphire, plastic orpolymer, or any other suitable material that is substantiallytransparent over at least a portion of the visible electromagneticspectrum. “Substantially transparent” in this context is functionallydefined in that the amount of light transmitted through the substrate issufficient to yield a visually pleasing ornamental, decorative, orjewelry article. The level of transmissivity needed varies according tothe typical environment in which the article is intended to bedisplayed. For example, when displayed in a sunlit environment, lowertransmission can be sufficient relative to that needed for display underrelatively dimmer interior lighting. The substrate can be colorless andclear (substantially full transmission over the entire visiblespectrum), can appear gray (less than full transmission that issubstantially uniform over the visible spectrum), or can appear colored(transmission that varies across the visible spectrum), as needed ordesired for a particular article displayed in a particular environment.

Ridges 104 and trenches 105 can be formed in or on the substrate 103 inany suitable manner, including but not limited to wet or dry etchingtechniques or, if the substrate is malleable, by stamping, molding, orsimilar mechanical processes. The ridges 104 and trenches 105 need nothave the rectangular cross-sectional form depicted in the drawings. Theridges and trenches can exhibit rounded corners or edges (as might oftenarise from a wet etch process, or from some types of stamping andmolding processes), tilted or slanted side walls (e.g., yieldingtrapezoidal ridges/trenches), or the ridges can have a sinusoidal orother curvilinear cross-sectional shape, with a smooth, continuoustransition between ridge and trench. The depth of the trenches 105(equivalently, the height of the ridges 104) can be varied to controlthe fraction of incident light that is diffracted by the grating. If thetrench width α and the ridge width β are comparable to one another andif the trench depth γ is selected (based on the refractive indices ofthe ridge material and any material filling the trenches) so that lightof a given wavelength transmitted through the substrate trench and ridgeregions accrue an optical phase difference of about π (or an odd integermultiple thereof), then a substantial fraction the incident light 101 isdiffracted to emerge in the ±1 orders of the output light 107 (thezero-order represents light transmitted directly through the gratingwithout being diffracted). Higher diffraction orders can appear and somefraction of the incident optical signal can be diffracted into thoseorders as well. Typically, when α≈β, a substantial fraction of thediffracted optical signal appears in the ±1 diffractive orders. If α andβ differ substantially, diffraction into higher diffractive orders canbe favored. The cross-sectional profile of the ridges can be selected toyield a desired distribution of diffracted intensity among variousdiffracted orders, using conventional techniques for diffraction gratingdesign.

In a many typical decorative, ornamental, or jewelry articles, theparameters α and β fall in the range of 0.2-3.0 μm, although largervalues are sometimes employed for diffracting light through relativelysmall angles. An etch depth γ of about 500-600 nm in a glass substrate(n≈1.45-1.50), that is viewed in transmission with the trenches filledwith air (n≈1), yields an approximate phase difference of about π forlight transmitted through the ridges or through the trenches andcorrespondingly efficient diffraction into the ±1 diffractive orders.More generally, relatively high diffraction efficiency arises whenγ≈λ/2Δn, where λ is a central representative wavelength of the opticalspectrum of interest, and Δn is the difference in the refractive indexof the ridges and trenches at that wavelength. Instead of air, thetrenches can be filled with adhesive, polymer, or other suitablytransparent material. For a diffraction grating to be used inreflection, the etch depth would typically be half of that used for atransmission grating to yield suitably optimized diffraction efficiency.The thickness d of the substrate 103 can be any convenient thicknessthat provides sufficient mechanical stability and compatibility withfabrication tools employed. If the diffraction grating is made on astandard wafer-type substrate using standard photolithographic tools, atypical wafer might have an industry-standard thickness such as 0.675 mmfor a 150 mm diameter wafer.

FIG. 2 illustrates schematically an exemplary multi-faceted diffractivestructure. The diffractive structure comprises multiple facets 203.Within each facet 203, diffractive grating “lines” (straight lines,curves, etc.) are formed in a substrate 201. FIG. 1B can be taken as across section of the ornament of FIG. 2 showing a region within onefacet cut perpendicular to that facet's diffractive contours (i.e.,grating lines). In some facets (e.g., facet 205), diffractive contourscan cross while remaining within the scope of the present disclosure orappended claims. When grating lines cross, diffractive features of thegrating (i.e., the elevated and recessed regions of the grating surface)can resemble posts, holes, polygons, dots, or other shapes rather thanonly ridges separated by trenches. The exemplary cross-sections shown inthe drawings can be viewed as cross-sections of these more generalizedelevated and recessed areas of the grating surface, rather than onlytransverse cross sections of elongated trenches and grooves. Althoughthe elevated and recessed regions are referred to in the presentdisclosure as ridges and grooves, respectively, that is for convenienceof description only and not intended to limit the scope of thedisclosure or the appended claims. A diffraction grating comprising ageneralized arrangement of elevated and recessed regions of variousshapes, sizes, and positions can provide diffractive behavior moregeneralized and customized than that provided by, e.g., a grating havingonly straight, parallel grating lines. A transverse dimension L of thesubstrate 201 can range from millimeter-scale up to centimeter-scale forsome types of ornaments, (e.g., earring drops or other jewelry items),or can be significantly larger for an item intended to be hung in awindow like stained glass.

Multi-faceted decorative, ornamental, or jewelry articles can be madesubstantially as shown in the cross-section of FIG. 1B. However,significant drawbacks of that arrangement can be mitigated or eliminatedby the arrangements disclosed or claimed herein. Some of the drawbacksof the arrangement of FIG. 1B are: lack of a strong reflected signal;vulnerability of the diffraction grating to contamination, e.g., foreignmaterial entering trenches and disrupting designed phase differentials;a need to form fairly deep trenches (e.g., more than a few hundred nm)when using common substrate materials such as glass; and lack ofavailable polymers having refractive indices that would allow their useto fill and protect trenches in typical, low-cost substrates such asglass or plastic. That last problem arises because many convenientlyavailable polymers have refractive indices close to those of commonsubstrates; use of such polymers to fill the grating trenchessignificantly reduces the phase difference between ridge and trench,which either weakens the diffracted signal or required increase trenchdepth to achieve a strong diffracted signal.

A cross-section of an exemplary embodiment of a diffraction grating thatcan operate in both reflection and transmission is illustratedschematically in FIG. 3. As with FIG. 1B, the cross-sections of FIGS.3-7 can represent a single grating or a single diffractive facet of amulti-faceted diffractive structure. Except as noted below, dimensionalparameters and materials are typically similar to those described abovefor FIGS. 1A and 1B. The diffraction grating of FIG. 3 includes a layer301 of a material that has an optical transmissivity differing from thatof substrate 305. The layer 301 can comprise, for example, a reflectivemetallic or ceramic material (e.g., gold, silver, aluminum, titaniumnitride), a substantially opaque material, a colored dielectricmaterial, or a multi-layer reflective dielectric stack. If desired,layer 301 can be chosen to exhibit a transmissivity differentialrelative to the substrate 305 over only a limited spectral bandwidth,thereby limiting the spectral bandwidth over which the diffractivestructure is active. A multi-layer dielectric stack or a doped glasswith sharp absorptive spectral features are well suited for use in sucha scenario.

The layer 301 can be formed on substrate 305 by vapor phase deposition,chemical vapor deposition, or other suitable deposition or coatingprocess. Ridges 302 and intervening trenches 303 that comprise thediffraction grating can be formed by any suitable spatially selectivematerial processing technique, such as by photolithographic patterningof a photoresist layer over layer 301 and subsequent etching through thelayer 301 to expose the substrate 305 at the bottom of the trenches 303.Alternatively, conventional optical interference fringes can be employedwith a suitable photoresist for patterning, although such patterningenables more limited grating design options than photolithographicpatterning. The etch can be halted precisely upon reaching the surfaceof substrate 305, or can overshoot into the substrate to avoid the needfor precise etch control. It can be desirable to minimize such overshootto reduce required etch time.

The thickness τ of the layer 301 is sufficient to create a substantialdifferential between the optical transmissivity of the ridges 302 (thatat least partly comprise the material of layer 301) and trenches 303over at least a portion of the visible electromagnetic spectrum. Forweakly diffractive articles, a differential of only a few percent can besufficient. For strong diffraction, a larger differential can beemployed, including examples in which optical transmission throughridges 302 is nearly zero. If a metal layer 301 is employed (such asaluminum, silver, or gold), a layer about 30-100 nm in thickness wouldbe needed to substantially eliminate transmission through ridges 302.Thicker layers (metal or non-metal) can be employed provided an etchprocess is employed that can etch through the layer 301 to the substrate305. Thinner layers can be employed if weaker diffractive strength isdesired. In the case of a multilayer dielectric reflector stack, thethickness of layer 301 can range from about 250 nm up to several micronsdepending on the reflective properties that are desired. Instead offirst applying a continuous layer 301 to the substrate 305 and thenetching through layer 301 into the substrate 305 to create thediffraction grating, the trenches 303 can be etched directly into thesubstrate 305 and then a directional (i.e., non-conformal) depositionprocess directed from the side can be employed to coat the ridges 302while leaving the trenches 303 substantially free of layer 301.

The embodiment of FIG. 3 can provide several advantages over thearrangement of FIG. 1B. The arrangement of FIG. 1B typically providessubstantial diffraction only in transmission. Similarly, if layer 301reduces optical transmission but is not reflective, then the resultingarticle typically can provide a visually pleasing appearance bydiffraction only in transmission. However, if a reflective layer 301 isemployed to form the embodiment of FIG. 3, the resulting diffractivearticle can provide a visually pleasing appearance by diffraction intransmission or in reflection. The trenches 303 of the embodiment ofFIG. 3 need only extend through the layer 301 (perhaps as little as 30nm for a metal layer), and are therefore often substantially shallowerthan the trench depths typically required for the arrangement of FIG.1B. Shallower trenches 303 can be desirable due to reduced processingtime or a wider selection of suitable etch processes (e.g., wet etchprocesses). The trenches 303 of the embodiment of FIG. 3 can be filledwith transmissive material without substantially degrading thediffractive strength of the article. Filling the trenches 303 with astable polymer material or an inorganic dielectric material providesprotection of the diffractive surface of the article from damage (e.g.,scratches or other mechanical damage) or contamination (e.g., from dustor skin oils).

In an alternative (not shown) to the exemplary embodiment of FIG. 3, adiffraction grating exhibiting similar characteristics and advantagescan be formed by depositing the second material (having the differingtransmissivity) within trenches formed on a first substrate material(instead of forming the ridges with the second material). Such anarrangement can be more difficult to realize with many typicalfabrication techniques. In one example of such an arrangement, a thinlayer of epoxy or other polymer having a transmissivity sufficientlydifferent from the substrate can be applied (as a liquid precursor) tothe diffractive structure and confined upon curing primarily within thetrenches of the diffraction grating.

In a further adaptation of the exemplary embodiment of FIG. 3 that isillustrated schematically in FIG. 4, a second substantially transparentsubstrate 407 can be attached to substrate 305 with the diffractiongrating sandwiched between them. The thickness of the second substrate407 is not critical, but is sufficiently thick to provide adequateprotection for the diffraction grating on substrate 305. The secondsubstrate 407 is substantially transparent over at least a portion ofthe visible electromagnetic spectrum, to the extent that it transmits asufficient fraction of light diffracted by the diffraction grating onsubstrate 305 (in transmission or reflection) to yield a visuallyappealing article. The substrates 305 and 407 can be attached to oneanother using an adhesive layer 408 that is substantially transparent(over at least a relevant spectral region) and that fills the trenchesof the diffraction grating. Alternatively, an adhesive can be employedonly at the edges or perimeters of the substrates 305 and 407 (in whichcase the adhesive need not be transparent). The thickness s of theadhesive layer 408 can be made as small as practicable to conserveadhesive and to reduce potential optical interference effects betweenadjacent interfaces. The exemplary article of FIG. 4 is more robust thanthat of FIG. 1B. If needed or desired, anti-reflection coatings 409 canbe applied to one or both of the exterior surfaces of the two substrates305 and 407 to reduce or eliminate reflections that might otherwiseobscure optical effects produced by the diffractive structure. Suchanti-reflection coatings can be of any suitable type and can includesingle-layer and multi-layer dielectric stacks.

Another exemplary embodiment, that operates primarily in transmission,is illustrated schematically in FIG. 5. A surface layer 507 is depositedon a substrate 509. Both layers are substantially transparent over atleast a portion of the visible electromagnetic spectrum. In this examplethe surface layer 507 is deposited or otherwise formed on substrate 509and has a bulk refractive index that is differs from that of substrate509 (and is typically higher). Trenches are etched or otherwise formedin layer 507, leaving ridges at least partly comprising the material oflayer 507; the trenches and ridges form a diffraction grating, aspreviously described. The layer 507 can comprise a relativelyhigh-refractive-index transparent material (e.g., n>2) such as titaniumdioxide, cerium oxide, silicon nitride, or other suitable high-indexmaterial; alternatively, layer 507 can comprise a lower index materialsuch as sapphire or silicon oxynitride (SiN_(x)O_(y)). It isadvantageous for the layer 507 to have a refractive index at least 0.2larger than the refractive index of a polymer used to fill the trenchesof the resulting diffraction grating (see below). For maximaldiffractive strength, the thickness of Layer 507 and the depth of thetrenches are selected so that a phase difference of about π (or an oddinteger multiple thereof) accrues between light transmitted through theridges and light transmitted through the trenches, as describedpreviously for the arrangement of FIG. 1B. A different phase differencecan be employed if less diffractive strength is desired. In contrast tothe arrangement of FIG. 1B, the larger index of the ridges in theembodiment of FIG. 5 (due to inclusion of material from high-index layer507) enables a smaller etch depth to produce a given phase difference.That phase difference and smaller etch depth can still be realized whenthe trenches are filled with epoxy or other suitable polymer 503,because of the index contrast between the polymer and the high-indexmaterial of layer 507. In an example wherein an e-beam-deposited film oftitanium oxide (n≈2.3) forms layer 507 and an epoxy layer 503 (n1.5)fills the trenches, the thickness τ of layer 507 of about 300 nm isadequate for strong diffraction, assuming the trenches are etched mostor all of the way through the layer 507. As with the example of FIG. 4,the example of FIG. 5 includes a second substrate 501 attached to thediffraction grating by layer 503. The second substrate 501 protects thediffraction grating from damage or contamination, as describedpreviously. Anti-reflection coatings 505 can be employed on one or bothsubstrate 501 and 509, if needed or desired. The exemplary embodiment ofFIG. 5, typically can be arranged to provide strong diffraction intransmission, but does not typically exhibit substantial diffractivestrength in reflection.

In the exemplary embodiment of a reflective diffractive articleillustrated schematically in FIGS. 6A and 6B, a diffraction grating 601is formed (by photolithographic etching or other suitable processingmethod) as a series of ridges and trenches that form a surface reliefstructure on a substantially transparent substrate 602. The substratecan comprise sapphire, fused silica, glass, plastic, or other suitabletransparent material. A reflective layer 603 (metallic or otherreflective material) is formed over the diffraction grating 601 bysputtering, e-beam vacuum deposition, or other suitable coating ordeposition method. Light propagating through the substrate 602 andincident on the diffraction grating 601 from within the substrate 602 isdiffracted in reflection, and the light thus diffracted propagates backthrough substrate 602 and out of the article.

In the embodiment of FIG. 6A, the reflective layer 603 is sufficientlythin, e.g., 10-500 nm, so that its upper surface approximates the etchedsurface relief structure of the diffraction grating 601. The thicknessof the layer 603 that preserves the surface relief structure while alsoproviding sufficient reflectivity varies according to the method ortechnique employed to deposit layer 603. A relatively thinner layer isneeded if a substantially conformal deposition process is employed,i.e., one that coats the sides of the grating ridges with the samethickness as the tops of the ridges and the bottoms of the trenches (asshown in FIG. 6A). A relatively thicker layer (as shown in FIG. 6B) canbe employed if a highly directional or non-conformal deposition processis employed (i.e., one that preferentially coats the tops of the ridgesand the bottoms of the trenches). If such a directional process is usedat normal incidence to substrate 602, the surface relief structure ofthe grating 602 can be at least approximately replicated on the surfaceof layer 603, in some cases even if the trenches are filled by layer603. In either case, a protective, substantially transparent secondsubstrate 604 can be attached to the article on layer 603 using, e.g., alayer of epoxy or other substantially transparent polymer or adhesive605. Any suitable alternative means can be employed to attach substrate604 to the article. Instead of attaching a second substrate 604, layer603 and its surface relief structure can be coated (e.g., using e-beamvacuum deposition or other suitable method depending on the materialemployed) with a substantially transparent protective layer comprisingsilica, aluminum oxide, epoxy or other polymer, or other suitably robustor scratch-resistant material.

The diffraction grating 601 in the embodiments of FIGS. 6A and 6Bprovides diffraction (in reflection) of light incident on layer 603 fromwithin substrate 602 or from within substrate 604 (and layer 605, ifpresent). A visually pleasing display can therefore be viewed inreflection from either side of the article. Use of precious metals forthe reflective layer 603 (e.g., gold, platinum, silver, or others) orsemi-precious materials for the transparent substrates 602 and 604(e.g., sapphire, lead crystal or others) can enhance the attractivenessof the article. To achieve near maximal diffraction, the trenches of thegrating 601 can be made approximately a quarter-wavelength deep, thewavelength referring here to the in-medium (substrate 602, substrate604, or layer 605 as appropriate) wavelength near the middle of therelevant spectral band (typically 500-550 nm if the entire visiblespectrum is relevant). Trenches deviating from that quarter-wavelengthalso provide diffraction, but at correspondingly lower efficiency orshifted to a different center wavelength. All such variations shall fallwithin the scope of the present disclosure or appended claims.

The exemplary embodiment of FIG. 7 is a variant of those of FIGS. 6A and6B. In FIG. 7, a diffraction grating 701 comprising ridges and trenchesis formed on a substantially transparent substrate 702. Substrate 702can comprise sapphire, fused silica, plastic, or other suitabletransparent material. A reflective layer 703 (metallic or otherreflective material) is deposited, using sputtering, e-beam vacuumdeposition, or other suitable coating or deposition method, over thediffraction grating 701. The reflective layer 703 is sufficiently thickto fill the trenches of the diffraction grating 701 and to provide arelatively flat (or at least substantially non-diffractive) uppersurface. The thickness of layer 703 need not be controlled withparticular precision, provided that it is thick enough to provide thedesired level of reflectivity. The diffraction grating 701 in thisembodiment can diffract light incident only from within substrate 702;light incident on the other surface of layer 703 (i.e., from outsidesubstrate 702) is not typically diffracted. A protective secondsubstrate 704 can be attached to the article over layer 703, using alayer 705 of epoxy or other adhesive or using any other suitable means.Alternatively, layer 703 can be coated (e.g., using e-beam vacuumdeposition or other suitable methods) with a substantially transparentprotective layer comprising silica, aluminum oxide, or other suitablyrobust or scratch-resistant material. If the reflective layer 703 issufficiently robust, or if in use it will not be exposed to theenvironment, a protective layer (deposited or attached) can be omittedaltogether.

Because the visually pleasing diffracted light pattern can be viewedonly from one side of layer 703 (through substrate 702), the embodimentof FIG. 7 is suitable for use in jewelry of other decorative orornamental articles in which only one side of the article is typicallyvisible. For example, the article of FIG. 7 could be mounted in a ringso that only one side of the article is visible.

In various exemplary embodiments, a diffraction grating is used only inreflection either from one surface of the grating or from both surfacesof the grating. In other exemplary embodiments, a diffraction grating isused in both reflection and transmission, with light incident on one orboth surfaces of the grating. In still other exemplary embodiments, adiffraction grating is used only in transmission. For a diffractiongrating intended to be used only in reflection from only one of itssurfaces, a transparent or non-transparent substrate can be employed tosupport the grating on its non-incident surface. A substrate supportingthe reflective grating on its incident surface (which thereforetransmits both incident and diffracted optical signals) is substantiallytransparent. If used in transmission, in both transmission andreflection, or in reflection from both grating surfaces, then anysubstrate supporting the grating on either grating surface must besubstantially transparent. In some exemplary embodiments, thediffraction grating can be positioned between two substrates. In thosecases at least one of the substrates is substantially transparent, andboth substrate are substantially transparent if the “sandwiched” gratingis used in transmission or in reflection from both surfaces.

An exemplary embodiment of a diffractive article is illustratedschematically in FIG. 8. A visually pleasing article is achieved in thisexample by a combination of refraction, diffraction, and reflection. Asubstrate 801 comprises lead crystal, glass, a gemstone (precious orsemi-precious), plastic, or other at least partially transparentmaterial and provides a number of faceted reflective/refractivesurfaces. On at least one facet, typically (but not necessarily) a largeone as is found in rhinestones and similar decorative articles, adiffractive structure 803 is formed or attached. The diffractivestructure can be etched or molded directly into the substrate. Ifmolded, heated glass or polymer or other at least partially transparentmaterial is shaped by a mold having at least one wall that is patternedaccording to the desired diffractive structure. Alternatively, if thesubstrate is a hard material like glass or sapphire or otherappropriately transparent material, a thin layer of deformable polymersuch as acrylic, polycarbonate, or PET (polyethylene terephthalate) canbe deposited on a facet and then patterned by stamping, molding, orother suitable method. In one example, a stamp bearing a surface ispatterned according to the desired diffractive structure is pressedagainst the deformable polymer with sufficient force and at adequatetemperature so that the pattern is transferred to the polymer. Thedeformable layer can be as thin as approximately one-half micron or canbe as thick as is convenient for fabrication and handling. Thediffractive pattern depth is typically about a quarter-wavelength formid-band light as measured in the layer material. The deformablematerial should be sufficiently transmissive to produce a visuallypleasing display.

Regardless of the manner in which the diffractive pattern is formed onone or more facets of the substrate 801, the resulting diffractiongrating can be of any suitable arrangement, including a single grating,a multi-faceted grating, or any of the arrangements disclosed herein orin the incorporated references. Regardless of the manner in which thediffraction grating is formed on one or more facets of substrate 801, areflective layer 807 can be deposited over grating 803 on thediffractive facet with sufficient depth to reflect a desired fractionlight incident from within substrate 801. The reflective layer 807 cancomprise a reflective metal (e.g., gold, silver, aluminum, and so on) orcan comprise one or more layers of dielectric material suitably robustor convenient to apply.

The embodiment of FIG. 8 can be particularly pleasing in appearancebecause it combines refractive/reflective effects long prized ingemstones and crystals with diffractive effects. Diffractive effectsoften accentuate fire and increase the spread of angles over whichoutput light is generated and observable. Decorative articles arrangedin a manner similar to that shown in FIG. 8 typically exhibit varying,somewhat subdued colors nearly constantly as an observer moves relativeto it. In contrast, a classic faceted gem tends to produce brief burstsof color as the angle of observation changes.

While layer 807 is shown in FIG. 8 as having a substantially flat (i.e.,non-diffractive) bottom surface (for example, arranged as in FIG. 7),layer 807 can instead be arranged in a manner similar to the embodimentsof FIG. 6A or 6B) so that diffraction occurs for light incident on bothsides of layer 807. A protective additional layer or a protectiveadditional substrate can be applied over the reflective layer 807, ifneeded or desired. Alternatively, a second faceted or curved substrate,perhaps similar to substrate 801, can be attached over grating 803 (andlayer 807, if present), to provide reflective or refractive redirectionof incident and diffracted optical signals on both side of the grating.

An example of such an embodiment is illustrated schematically in FIGS.9A and 9B. A single- or multi-faceted diffraction grating can be formedto diffract incident light in reflection, transmission, or a combinationof reflection and transmission, a variously described herein and isenclosed within curved substrates on both sides. In an exemplary processfor fabricating the item of FIGS. 9A and 9B in volume, a diffractivestructure can be formed to cover an area of a first substrate that ismany times larger than the finished article. A second, similarly sizedsubstrate is attached over the grating layer. The resulting large“sandwich” structure can then be divided into individual articles usingany suitable cutting tools or implements, such as a dicing saw forcutting straight-line patterns yielding polygonal articles, or a coringtool or hole saw for producing circular articles. The separated articlescan be finished or polished in any suitable way (e.g., in a rotary orvibrational tumbler) to yield the final product having smoothed cornersand edges and polished surfaces similar to precious or semi-preciousstones used in jewelry settings.

Rather than forming a diffraction grating directly on a facet of a gem,bead, rhinestone, or other decorative article, a diffractive gratingpattern can be stamped, embossed, or molded onto a flexible film, suchas a polymer or metal film. The patterned film is then attached (e.g.,using adhesive) to the desired location on the decorative article(illustrated schematically in FIG. 10). A metal film thus patterneddiffracts only in reflection (from one or both sides, depending on thearrangement and the nature of the article to which the metal film isattached). A transparent film thus patterned can have a reflectivecoating applied (metallic or otherwise) to enhance diffraction inreflection. As described elsewhere, the patterned grating film can bearranged to diffract only on one side or to diffract on both sides, byreflection (from both sides) or by a combination of transmission andreflection (from one or both sides). If arranged to diffract from bothsides, the diffractive film can be adhered, for example, between twodecorative articles such a flatback rhinestones to produce a richlyfaceted item with exquisite fire.

It is intended that equivalents of the disclosed exemplary embodimentsand methods shall fall within the scope of the present disclosure orappended claims. It is intended that the disclosed exemplary embodimentsand methods, and equivalents thereof, may be modified while remainingwithin the scope of the present disclosure or appended claims.

For purposes of the present disclosure and appended claims, theconjunction “or” is to be construed inclusively (e.g., “a dog or a cat”would be interpreted as “a dog, or a cat, or both”; e.g., “a dog, a cat,or a mouse” would be interpreted as “a dog, or a cat, or a mouse, or anytwo, or all three”), unless: (i) it is explicitly stated otherwise,e.g., by use of “either . . . or”, “only one of . . . ”, or similarlanguage; or (ii) two or more of the listed alternatives are mutuallyexclusive within the particular context, in which case “or” wouldencompass only those combinations involving non-mutually-exclusivealternatives. For purposes of the present disclosure or appended claims,the words “comprising,” “including,” “having,” and variants thereofshall be construed as open ended terminology, with the same meaning asif the phrase “at least” were appended after each instance thereof.

1. An article comprising at least one surface bearing at least oneoptical diffraction grating, wherein: (a) the article comprises a firstdielectric material that is substantially transparent over at least afirst region of the visible electromagnetic spectrum; (b) thediffraction grating comprises a plurality of elevated spatial regionsand recessed spatial regions; (c) the diffraction grating furthercomprises a second dielectric material that is substantially transparentover at least a portion of the first spectral region and thatsubstantially covers the elevated and recessed regions; (d) thediffraction grating further comprises a third dielectric material havingoptical transmissivity differing from that of both the first and seconddielectric materials or having a refractive index differing from that ofboth the first and second dielectric materials over at least a portionof the first spectral region; (e) either (i) at least a portion of eachelevated region comprises the first dielectric material and the thirddielectric material at least partly fills the recessed regions or (ii)at least a portion of each elevated region comprises the thirddielectric material and the second dielectric material substantiallyfills the recessed regions; and (f) the third dielectric material isabsent from certain areas of the diffraction grating so that the firstand second dielectric materials are in contact in those areas from whichthe third dielectric material is absent.
 2. The article of claim 1wherein the elevated regions comprise elongated ridges and the recessedregions comprise trenches between the ridges.
 3. The article of claim 1wherein the article comprises a volume of the first dielectric materialhaving at least one faceted or curved surface.
 4. The article of claim 1further comprising a mount attached to the first dielectric material,wherein the article is an item of jewelry.
 5. The article of claim 1wherein the second dielectric material comprises a polymer.
 6. Thearticle of claim 5 further comprising a substrate positioned on thesecond dielectric material with the second dielectric material betweenthe substrate and the first dielectric material, wherein the substrateis substantially transparent over at least a portion of the firstspectral region.
 7. The article of claim 1 wherein the third dielectricmaterial exhibits optical transmissivity less than that of both thefirst and second dielectric materials over at least a portion of thefirst spectral region.
 8. The apparatus of claim 7 wherein the thirddielectric material comprises a reflective layer so that the diffractiongrating is arranged to diffract incident light both in transmission andin reflection.
 9. The article of claim 7 wherein the third dielectricmaterial is substantially opaque over at least a portion of the firstspectral region.
 10. The article of claim 7 wherein the third dielectricmaterial exhibits optical absorption over at least a portion of thefirst spectral region.
 11. The article of claim 1 wherein the thirddielectric material exhibits a refractive index greater than that ofboth the first and second dielectric materials over at least a portionof the first spectral region.
 12. The article of claim 11 wherein athickness of the third dielectric material and the respective refractiveindices of the first, second, and third dielectric materials result in arelative phase difference of about π between light propagating throughthe recessed regions and light propagating through the elevated regions,the light propagating at a selected design optical frequency.
 13. Thearticle of claim 11 wherein the refractive index of the third dielectricmaterial exceeds that of both the first and second dielectric materialsby more than about 0.2.
 14. The article of claim 1 wherein the recessedregions comprise etched portions of the first dielectric material. 15.The article of claim 1 wherein the third dielectric material is absentfrom the elevated regions so that the first and second dielectricmaterials are in contact in the elevated regions.
 16. The article ofclaim 1 wherein the third dielectric material is absent from therecessed regions so that the first and second dielectric materials arein contact in the recessed regions.
 17. The article of claim 1 whereinthe third dielectric material is absent from sidewalls connecting theelevated and recessed regions so that the first and second dielectricmaterials are in contact at the sidewalls.
 18. The article of claim 1wherein the third dielectric material exhibits optical transmissivitygreater than that of both the first and second dielectric materials overat least a portion of the first spectral region.
 19. The article ofclaim 1 wherein the third dielectric material exhibits a refractiveindex less than that of both the first and second dielectric materialsover at least a portion of the first spectral region.